The control system of the invention is particularly suited to operate in conjunction with cooking and holding ovens of the type described in U.S. Pat. Nos. 3,521,030 and 3,800,123, both of which are assigned to the present assignee.
The oven described in the above-mentioned patents includes one or more electric cables encased in the walls of the oven, and which extend around the interior compartment. The oven described in the patents includes an appropriate electric circuit for energizing the electric cable to cause it to generate heat in the oven. The circuit includes an appropriate timer which serves to reduce the current flow in the cable after a preset time interval, so as to reduce the internal oven temperature from a cooking level to a holding level. As described in the patents, the cooking temperature and holding temperature in the oven may be preset by the user, and the time of the cooking interval may also be preset. An important feature of the oven described in the patents is that when the cooking cycle is completed, the oven automatically drops its internal temperature to a desired holding level which is preset by the user, so that there is no need to transfer the food from the oven to a holding warmer.
The solid state control system of the present invention is advantageous in that it does not depend on any particular time interval to establish the cooking cycle. Instead, the control system includes a probe which is inserted into the meat itself, and the cooking interval is determined by the internal temperature of the meat, so that the meat, in all instances, is cooked to exactly the degree desired, regardless of ambient conditions, and is held in a warm state within the oven until needed.
By the system of the invention, the meat is first cooked at a preset temperature in the oven until a predetermined internal meat temperature is reached, and then the oven temperature is automatically gradually reduced for several hours while the meat is being cooked. This gradual reduction in oven temperature continues until a particular holding temperature of, for example, 138.degree. F is reached, and the oven is maintained at the holding temperature until the meat is removed. This holding temperature of 138.degree. F has been found to be appropriate for maximum enzyme action for tenderizing the meat while preventing additional cooking or bacteria growth.
By the use of the control system of the invention, various types of meats can be cooked to a desired state and held hot until needed, on a completely automatic basis, and merely by placing the meat in the oven, inserting a probe into the meat, and pushing a selected pushbutton. The cooking cycle is determined, as mentioned above, not on a time basis, but on the basis of the actual internal temperature of the meat, so that under all conditions, the user has complete assurance that the meat will be cooked to exactly the state selected by him, as determined by the actuated pushbutton.